linux-kernel - Re: [PATCH] audit_tree: keep inode pinned

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Message-ID: <20141112173007.GB28076@madcap2.tricolour.ca>
Date:	Wed, 12 Nov 2014 12:30:07 -0500
From:	Richard Guy Briggs <rgb@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	Eric Paris <eparis@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-audit@...hat.com
Subject: Re: [PATCH] audit_tree: keep inode pinned

On 14/11/05, Miklos Szeredi wrote:
> On Wed, Nov 5, 2014 at 5:58 PM, Richard Guy Briggs <rgb@...hat.com> wrote:
> > On 14/11/04, Miklos Szeredi wrote:
> >> From: Miklos Szeredi <mszeredi@...e.cz>
> >
> > Hi Miklos,
> >
> >> Audit rules disappear when an inode they watch is evicted from the cache.
> >> This is likely not what we want.
> >>
> >> The guilty commit is "fsnotify: allow marks to not pin inodes in core",
> >> which didn't take into account that audit_tree adds watches with a zero
> >> mask.
> >>
> >> Adding any mask should fix this.
> >
> > Nice find!  Do you have a quick reproducer to detect this?
> 
> - reboot
> - add tree rule
> - echo 2 > /proc/sys/vm/drop_caches
> 
> drop_caches doesn't guarantee dropping the inode from the cache, but
> after a reboot it usually does.

Perfect, thanks!  That works as expected.  While I was at it, I checked
the audit_watch code and the pending "filter on process name" patches to
make sure they didn't have the same problem.

> Thanks,
> Miklos

- RGB

--
Richard Guy Briggs <rbriggs@...hat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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